Your crazy engine combos?

[RacnJsn95]

I've always been looking into making different stuff, with stuff that's available at the time. Even thinking outside the box, to use non-nissan parts. Anyone ever come up with something, that sounded good on paper, or even went ahead and build? Here was my latest big idea...

 

Going off the Jason Grey engine info page, for the Med. Block 2.4, I came up with this...

 

 

[LAYEDOUTB2K]

not exactly non nissan parts. but one thing ive always thought that is cool and cheap to do to an L18. if you bore it .080 over stock 280Z pistons will drop right in

[hang_510]

its a lot of work to stuff the crank into a L20 block.

ben pila has done(1st???) it, and a few ozdat guys, have not heard much good about it either...

the Z22 crank fitss w/o work, but has a shorter stroke

 

are L28 pistons a better choice?

 

play here w/ your details...

http://www.ozdat.com/ozdatonline/enginedesign/

 

ALL your info must match for it to work correctly

[RacnJsn95]

Looks like my idea works with the OZdat calculator, but it's got 13.27:1 compression with a 45.2cc head. NICE!

[hang_510]

might as well buy my forged domed (stock) L20 pistons then... :P

[banzai510(hainz)]

.080 over stock 280Z pistons will drop right in?????????

 

its really .040 over

 

280zx NON turbo are flatops and stock size is 86mm or 1mm(.039) over in a L18/20. Price is a killer if getting these from Nissan and havent seen a real supplier for these.

I have seen L18 4cc dished pistons from Rockauto.com 12159P (73 Datsun 610 ).

I have these installed in my 510 L16, bored over from 83 to 85mm (.080)

 

Pistons are in a Sealed Power box but made by sterling in the USA.

 

ck rockauto.com for price if still avail.

 

 

when it comes to 4x4 I like using cheap gas(in case your in a really rural area that uses cheap low octane gas, Like fucking Mexico!!!!!)

 

open chamber heads may have pinging issues with a raised compression

 

I believe Datsunfreak(texas) has some issues on his L20 with L18 pistons or flattops and a open chamber head????????????needs to run 94 octane

I see mostly 91 here in washington

Maybe he can elaborate more on this.

[hang_510]

and a open chamber head???

I see mostly 91 here in washington.

 

best we have is 91 down here too

i kept the CR <9.5:1 for that reason

 

the L-Z24 w/ U67 cruises fine on 87, but has significant loss of topend unless i use 91

[LAYEDOUTB2K]

i guess i was mistaken about the bore size but they do have the same pin to top of piston heights. the reason i brought it up was my dad ran mini stocks before in a 510 and they required stock internals in the class. the tech guys couldnt tell the difference because it was a "factory" piston

[SHADY280]

i had to use toyota rings on my 280zx, i bored it .040 over, and got the last set of pistons avail. (so i was told) for stock replacement. the ring set for the 280 was incorrect for the pistons, so the machine shop guy looked thru the book and found the yota rings would work just fine. that and i decked my p79 head ..080!!! i had my comp ratio at 11.8:1 on the street for a awhile. had to run 94 plus booster, but man did it move. ive since lowered it with a 2mm gasket to 10.8:1. i can get away with 91 now, until i bump the timing for racing. the race 280 motor should be at aboot 12:1 ish, i hope.

[datzenmike]

Looks like my idea works with the OZdat calculator, but it's got 13.27:1 compression with a 45.2cc head. NICE!

 

86mm bore X 96 stroke

zero deck

1.2mm crushed gasket = 6.9cc

45.2cc head

 

This combo works out to 11.696 to 1 compression ratio.

 

With a 41cc P nut head it's 12.63 to 1.

[RacnJsn95]

That sounds a little more resonable... For some reason when I think of crushed gasket thickness I always think in inches... When I put it in the calculator, I put .040 for the thickness, resulting in 13.275:1. lol

 

I thought my Z22 crank combo was gonna be around 10.5:1, but with the correct gasket thickness it's going to be between 9.5 and 10.4 with a closed chamber head, but I wont know untill after I mill the pistons how many cc's the dish will be.

[pope_face]

Ok, I'm hoping to get a good working engine in my truck, so hopefully I don't ruin your crazy combo thread... But does anyone have any recommendations for octane for a particular compression? I know it'll run best at the highest octane available, but I'm just curious as to how low you can go and still have the engine run well... from what I can tell, a CR of less than 10.0:1 will run well on 91, and any CR higher than that won't run as well unless you use 94+ octane, correct?

 

Also... pardon my inexperiance with terminology, but can anyone tell me what the terms open-chamber, closed-chamber, and peanut head refer to when talking about heads? And which one is the U67 off the L20B? It seems to be the higher-volume head, which makes it open-chamber?

 

I believe Datsunfreak(texas) has some issues on his L20 with L18 pistons or flattops and a open chamber head????????????needs to run 94 octane

 

The Ozdat gives me a deck clearance of 0.45 mm and a CR of 9.211:1 on a stock L20B with a 1.25 mm gasket, U67 head, and L18 pistons... is this setup feasible, and would it run well on 91, or would I have to run 94?

[RacnJsn95]

I wonder how correct the oZdat thing is... The l20b in my 620 is +.75 overbore, L18 pistons, with a 41 cc head, and it says I have 10.013:1 compression ratio... I was running it on 87 octane without a single problem. Can anyone confirm how correct the ozdat calculator is? I thought I had around 9.5-9.75:1.

 

I've read of Z car guys running in the 11:1 range and still running on 91 octane, but I dont know if I believe it... My 68 Chevelle has 10.5:1 and I have to run 91 or better.

 

The heads with the smaller volume combustion chamber are refered to closed chamber, or peanut heads. Larger volume, refered to open chamber... If you see the chambers side by side, it's very easy to tell the difference. I wish I had a pic handy... The closed/peanut head chamber is kind of "heart" or "kidney shaped", where as the open chamber is... more open.

 

There are rumors that say running a high compression ratio with an open chamber head, will result in pinging(detonation), sometimes even with good gas. It's said that the closed/peanut head has a better "quench", and is more efficient.

 

IMO anything under 10:1 you can get away running 87 or 89 octane, unless it pings, if it does, just go up in octane untill it stops. Unless of course you're running a supercharger or turbo, then you'll naturally want to run better gas.

[pope_face]

Thanks for the response... I remember seeing pictures of "peanut" shaped heads, so I thought that might be what it was referring to... Always good to check though.

 

As for the pinging... I might have read it somewhere, but I don't think I payed much attention as I didn't think it would concern me too much... I didn't really think about anything like bumping compression until today, to tell the truth. As for Ozdat, I have no idea how accurate it is either, but it's all I have to go on for now... But, if I switch to the closed-chamber head, I'll have the same setup as you, save for the overbore... so if you can run 87 without issues, I suppose I'll get pretty good performance with 91.

 

As far as a turbo goes, I'm planning another engine build at some point in the future... a turbo carbed engine. I know it's been done, and there's writeups on it, but it's more for experiance and getting to brag that I have a turbocharged engine. As for superchargers, it'd be interesting to do one, but they've never been my thing... I've always preferred the sound of a turbo spooling up... :D

[datzenmike]

That sounds a little more resonable... For some reason when I think of crushed gasket thickness I always think in inches... When I put it in the calculator, I put .040 for the thickness, resulting in 13.275:1. lol

 

I thought my Z22 crank combo was gonna be around 10.5:1, but with the correct gasket thickness it's going to be between 9.5 and 10.4 with a closed chamber head, but I wont know untill after I mill the pistons how many cc's the dish will be.

 

The crushed gasket is about 1.2mm or 0.047". You're close enough.

 

Also... pardon my inexperiance with terminology, but can anyone tell me what the terms open-chamber, closed-chamber, and peanut head refer to when talking about heads? And which one is the U67 off the L20B? It seems to be the higher-volume head, which makes it open-chamber?

 

 

 

The Ozdat gives me a deck clearance of 0.45 mm and a CR of 9.211:1 on a stock L20B with a 1.25 mm gasket, U67 head, and L18 pistons... is this setup feasible, and would it run well on 91, or would I have to run 94?

 

I got 9.31 close enough.

 

To expand on the open/closed chamber:

 

An open chamber (45.2cc)would have little or no quench area (I'll get to that later) and would be round and as wide as the bore on the cylinder.

 

A closed (41cc), or P nut head, are the same thing, although the P nut also refers to the roughly P nut shape, which does not match the round size of the cylinder bore at all. Obviously there will be areas where the piston reaches Top Dead Center and is tight against the head surface. These areas are called the quench or squish areas and are very important for the effect they have on the fuel air mixture.

Just as the piston reaches TDC on compression the fuel/air mixture is violently pinched between the rising piston and the flat head surface, and forced into the remaining open portion of the chamber. This causes a desirable turbulence or swirl which further mixes or homogenizes the fuel and air. Now this in turn has two important effects.

 

1 the burn is more efficient (more power increased mileage) with better mixed fuel and air, (no rich or lean areas) and this leads to...

2 more even cylinder temperatures and reduced 'hot spots' which are the prime cause of pre-ignition.

 

So it is possible to run a higher compression ratio without increasing the octane of your gas.

[pope_face]

Bah! Thanks Mike... That increased my engine knowledge by about 15%...

 

Looks like that'll be the setup I'll be persuing then... hopefully I can piece together the parts sometime over the next couple months... Then again, two weeks ago I was happy just changing the gaskets on my J13, now here I am planning a fully rebuilt engine and discussing compression and fuel octane and the pros and cons of various cylinder head and piston combos... I wonder what next week will bring...

[SHADY280]

so what are the best heads for turbo setups? and what are the best for n/a setups. i cant remeber what my truck has, but knowing my luck its the crappist one!! it always happens that way.

[RacnJsn95]

The crushed gasket is about 1.2mm or 0.047". You're close enough.

 

Yeah, but the oZdat calculator, reads in mm... I put .040 in, it reads it as .040mm. It was close, but not close enough for Oz :P

 

So you think the setup in my 620 now is really 10:1?

[banzai510(hainz)]

closed chamber heads are less prone to detonation.

 

In my 521 I had a L16 with stock dished ipistons and open U67 it would PING

later with flattops it would PING

 

my closed chamber heads dont ping on regular gas (L16/18)

[SHADY280]

i kinda hoped there would be some casting numbers involved. the site where ya build your engines combos dont tell ya the best, they just give some numbers, and they arent always the "best" head that has the best performance in the real world.

[datzenmike]

so what are the best heads for turbo setups? and what are the best for n/a setups. i cant remember what my truck has, but knowing my luck its the crappist one!! it always happens that way.

 

A good question. It all comes down to breathing on, a normally aspirated head. Small valves and/or runners and a low lift short duration cam will severely restrict the motors ability to breathe. It just has to work harder for less output.

 

Enter the turbo 'The Great Equalizer'. When fuel/air is forced into the cylinder by a turbo, the motor now doesn't have to work hardly at all and all the fuel/air it needs for power is available. Larger valves, porting, bigger cams are not as important on a turbo motor. In fact a bigger, high overlap cam is a waste as the turbo will actually push fuel/air right past both open valves and out the exhaust port.

 

At about 7.5 lbs of boost, theoretically you are cramming an extra 50% more air into your engine and the compression will rise in direct proportion. If you are running 10 to 1, theoretically you are now 15 to 1 (probably less from losses and inefficiencies) but you can see that pinging will be a BIG problem. A good answer is to reduce the C/R to, say 7.5. this would give a boosted C/R of around 11 to 1, better. But as always you don't get something for nothing. At less than boost pressures you are driving a 7.5 compression dog with poor performance.

 

Running a high compression motor WITH turbo gives best overall performance, but extreme cylinder temperatures will be a problem under boost. Enter the inter-cooler. Whenever air is compressed into a smaller space, the temperature rises. If we take the turbo compressed air (which is now hotter than ambient) and run it through another radiator (just like the cooling system) we can lower it's temperature before it enters the motor. Cooler air is denser, and you can cram more into the cylinder. Reduced temperatures will lower the tendency of a motor to 'ping' or pre-ignite. Heat is the mortal enemy of a turbo motor and per-ignition will destroy it in a frighteningly short time.

[SHADY280]

all that i know, after all it is my job (mechanic) but im just not familiar with the l series 4 banger head casting numbers. i figured you gurus would know. i only know all the z car L6 casting numbers, and which is good for what. the reason i wanna know, is im prolly gonna turbo the 1.8 in my truck, with a z intake maini, shortened. im gonna run a t25,t28 turbo, and put in some boost, my numbers are not yet determined until the build starts, i just want to get a good head built up, or start to look for the right on to start with. the rest is just build.

[datzenmike]

I don't know if there are any fast and true P-nut head numbers but this:http://www.the620.com/html/tech/head_ID_2.htm will give you some info on what to expect and what to look out for.

[Fineline]

My closed chamber w-58 head cc'd at 43.2

 

[pope_face]

Bah, that's sexy... why the larger volume? Are you trying to bring the compression down for a particular project? Or is this the normal volume on these heads... Ozdat says 41 cc, but the general concensus seems to be that the site is not as accurate as it should be...